I'm wondering if anyone knows what the exact aspect ratio would be of DVX100 footage with the widescreen matte turned on. In trying to measure it in Final Cut, applying the 1.66:1 and 1.70:1 mattes don't do anything, but the 1.78:1 matte crops off a slight additional amount of any shot. Using Compressor, the 1.75:1 matte also crops off slightly more footage than was originally matted by the letterbox.
If it helps, here are the numbers that Compressor provides:
Using 1.66:1 matte crops the top and bottom to a value of 47. Using a 1.75:1 matte crops the top and bottom to 57 and selecting 'Letterbox Area of Source' crops the top and bottom to 54.